# Varnish
Plugin: python.d.plugin
Module: varnish
## Overview
This collector monitors Varnish metrics about HTTP accelerator global, Backends (VBE) and Storages (SMF, SMA, MSE) statistics.
Note that both, Varnish-Cache (free and open source) and Varnish-Plus (Commercial/Enterprise version), are supported.
It uses the `varnishstat` tool in order to collect the metrics.
This collector is supported on all platforms.
This collector only supports collecting metrics from a single instance of this integration.
`netdata` user must be a member of the `varnish` group.
### Default Behavior
#### Auto-Detection
By default, if the permissions are satisfied, the `varnishstat` tool will be executed on the host.
#### Limits
The default configuration for this integration does not impose any limits on data collection.
#### Performance Impact
The default configuration for this integration is not expected to impose a significant performance impact on the system.
## Metrics
Metrics grouped by *scope*.
The scope defines the instance that the metric belongs to. An instance is uniquely identified by a set of labels.
### Per Varnish instance
These metrics refer to the entire monitored application.
This scope has no labels.
Metrics:
| Metric | Dimensions | Unit |
|:------|:----------|:----|
| varnish.session_connection | accepted, dropped | connections/s |
| varnish.client_requests | received | requests/s |
| varnish.all_time_hit_rate | hit, miss, hitpass | percentage |
| varnish.current_poll_hit_rate | hit, miss, hitpass | percentage |
| varnish.cached_objects_expired | objects | expired/s |
| varnish.cached_objects_nuked | objects | nuked/s |
| varnish.threads_total | None | number |
| varnish.threads_statistics | created, failed, limited | threads/s |
| varnish.threads_queue_len | in queue | requests |
| varnish.backend_connections | successful, unhealthy, reused, closed, recycled, failed | connections/s |
| varnish.backend_requests | sent | requests/s |
| varnish.esi_statistics | errors, warnings | problems/s |
| varnish.memory_usage | free, allocated | MiB |
| varnish.uptime | uptime | seconds |
### Per Backend
This scope has no labels.
Metrics:
| Metric | Dimensions | Unit |
|:------|:----------|:----|
| varnish.backend | header, body | kilobits/s |
### Per Storage
This scope has no labels.
Metrics:
| Metric | Dimensions | Unit |
|:------|:----------|:----|
| varnish.storage_usage | free, allocated | KiB |
| varnish.storage_alloc_objs | allocated | objects |
## Alerts
There are no alerts configured by default for this integration.
## Setup
### Prerequisites
#### Provide the necessary permissions
In order for the collector to work, you need to add the `netdata` user to the `varnish` user group, so that it can execute the `varnishstat` tool:
```
usermod -aG varnish netdata
```
### Configuration
#### File
The configuration file name for this integration is `python.d/varnish.conf`.
You can edit the configuration file using the `edit-config` script from the
Netdata [config directory](https://github.com/netdata/netdata/blob/master/docs/configure/nodes.md#the-netdata-config-directory).
```bash
cd /etc/netdata 2>/dev/null || cd /opt/netdata/etc/netdata
sudo ./edit-config python.d/varnish.conf
```
#### Options
There are 2 sections:
* Global variables
* One or more JOBS that can define multiple different instances to monitor.
The following options can be defined globally: priority, penalty, autodetection_retry, update_every, but can also be defined per JOB to override the global values.
Additionally, the following collapsed table contains all the options that can be configured inside a JOB definition.
Every configuration JOB starts with a `job_name` value which will appear in the dashboard, unless a `name` parameter is specified.
Config options
| Name | Description | Default | Required |
|:----|:-----------|:-------|:--------:|
| instance_name | the name of the varnishd instance to get logs from. If not specified, the local host name is used. | | yes |
| update_every | Sets the default data collection frequency. | 10 | no |
| priority | Controls the order of charts at the netdata dashboard. | 60000 | no |
| autodetection_retry | Sets the job re-check interval in seconds. | 0 | no |
| penalty | Indicates whether to apply penalty to update_every in case of failures. | yes | no |
| name | Job name. This value will overwrite the `job_name` value. JOBS with the same name are mutually exclusive. Only one of them will be allowed running at any time. This allows autodetection to try several alternatives and pick the one that works. | | no |